Measure Index Use衡量索引的使用

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Get Index Access Information with $indexStats使用$indexStats获取索引访问信息

Use the $indexStats aggregation stage to get statistics regarding the use of each index for a collection. 使用$indexStats聚合阶段获取有关集合中每个索引使用情况的统计信息。For example, the following aggregation operation returns statistics on the index use on the orders collection:例如，以下聚合操作返回orders集合上索引使用的统计信息：

db.orders.aggregate( [ { $indexStats: { } } ] )
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$indexStats

Return Query Plan with explain()使用explain()返回查询计划

Use the db.collection.explain() or the cursor.explain() method in executionStats mode to return statistics about the query process, including the index used, the number of documents scanned, and the time the query takes to process in milliseconds.在executionStats模式下使用db.collection.explain()或cursor.explain()，以返回有关查询过程的统计信息，包括使用的索引、扫描的文档数以及处理查询所需的时间（以毫秒为单位）。

Run db.collection.explain() or the cursor.explain() method in allPlansExecution mode to view partial execution statistics collected during plan selection.在allPlansExecution模式下运行db.collection.explain()或cursor.explain()，以查看在计划选择期间集合的部分执行统计信息。

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planCacheKey

Control Index Use with hint()控件索引与hint()一起使用

To force MongoDB to use a particular index for a db.collection.find() operation, specify the index with the hint() method. 要强制MongoDB为db.collection.find()操作使用特定索引，请使用hint()方法指定索引。Append the hint() method to the find() method. 将hint()方法附加到find()方法。Consider the following example:考虑以下示例：

db.people.find(
   { name: "John Doe", zipcode: { $gt: "63000" } }
).hint( { zipcode: 1 } )

To view the execution statistics for a specific index, append to the db.collection.find() the hint() method followed by cursor.explain(), e.g.:要查看特定索引的执行统计信息，请在db.collection.find()中附加hint()方法，后跟cursor.explain()，例如：

db.people.find(
   { name: "John Doe", zipcode: { $gt: "63000" } }
).hint( { zipcode: 1 } ).explain("executionStats")

Or, append hint() method to db.collection.explain().find():或者，将hint()方法附加到db.collection.explain().find()：

db.people.explain("executionStats").find(
   { name: "John Doe", zipcode: { $gt: "63000" } }
).hint( { zipcode: 1 } )

Specify the $natural operator to the hint() method to prevent MongoDB from using any index:为hint()方法指定$natural运算符，以防止MongoDB使用任何索引：

db.people.find(
   { name: "John Doe", zipcode: { $gt: "63000" } }
).hint( { $natural: 1 } )

Index Metrics索引度量

In addition to the $indexStats aggregation stage, MongoDB provides various index statistics that you may want to consider when analyzing index use for your database:除了$indexStats聚合阶段之外，MongoDB还提供了各种索引统计数据，您在分析数据库的索引使用时可能需要考虑这些数据：

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